From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with archive (Exim 4.43) id 1JCNNs-0007PD-KC for mharc-grub-devel@gnu.org; Tue, 08 Jan 2008 17:57:24 -0500 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1JCNNq-0007NI-U2 for grub-devel@gnu.org; Tue, 08 Jan 2008 17:57:22 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1JCNNp-0007Ly-5e for grub-devel@gnu.org; Tue, 08 Jan 2008 17:57:22 -0500 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1JCNNo-0007Lp-Ug for grub-devel@gnu.org; Tue, 08 Jan 2008 17:57:21 -0500 Received: from c60.cesmail.net ([216.154.195.49]) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_ARCFOUR_SHA1:16) (Exim 4.60) (envelope-from ) id 1JCNNo-0006YL-AN for grub-devel@gnu.org; Tue, 08 Jan 2008 17:57:20 -0500 Received: from unknown (HELO relay.cesmail.net) ([192.168.1.81]) by c60.cesmail.net with ESMTP; 08 Jan 2008 17:57:17 -0500 Received: from [192.168.1.21] (static-72-92-88-10.phlapa.fios.verizon.net [72.92.88.10]) by relay.cesmail.net (Postfix) with ESMTP id E7449618FE1 for ; Tue, 8 Jan 2008 17:57:16 -0500 (EST) From: Pavel Roskin To: The development of GRUB 2 In-Reply-To: <20080108202455.GA22878@thorin> References: <20080108105057.GA24604@thorin> <1199816665.30874.13.camel@dv> <20080108202455.GA22878@thorin> Content-Type: text/plain Date: Tue, 08 Jan 2008 17:57:16 -0500 Message-Id: <1199833036.21357.12.camel@dv> Mime-Version: 1.0 X-Mailer: Evolution 2.12.2 (2.12.2-2.fc8) Content-Transfer-Encoding: 7bit X-detected-kernel: by monty-python.gnu.org: Genre and OS details not recognized. Subject: Re: contradiction in boot/i386/pc/boot.S X-BeenThere: grub-devel@gnu.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: The development of GRUB 2 List-Id: The development of GRUB 2 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 08 Jan 2008 22:57:23 -0000 On Tue, 2008-01-08 at 21:24 +0100, Robert Millan wrote: > On Tue, Jan 08, 2008 at 01:24:25PM -0500, Pavel Roskin wrote: > > On Tue, 2008-01-08 at 11:50 +0100, Robert Millan wrote: > > > boot_drive_check: > > > jmp 1f /* grub-setup may overwrite this jump */ > > > testb $0x80, %dl > > > jnz 1f > > > movb $0x80, %dl > > > 1: > > > > > > However, if 0x80 is really "the only possible boot drive", that means the > > > test is pointless and can be replaced with: > > > > No, I was wrong, I misread "testb" as "cmpb". Values such as 0x81 are > > valid and should be preserved. > > Yeah I was going to point that.. > > > Please ignore my previous message. > > All of it, or just partly ? All of it, I'm afraid. However, it's possible to save 2 bytes if we get rid of the first short jump and overwrite the whole section (testb, jnz, movb) with NOPs for the floppies. We can save 4 more bytes if we do "orb $0x80, %dl" unconditionally for the hard drives. However, I'm not sure if there are BIOSes that pass 1 in %dl and how critical it would be if it becomes 0x81. That's something I'll rather not do without seeing the original bug reports. -- Regards, Pavel Roskin